Presently available imaging diagnostic apparatuses for capturing diagnostic images of patients include CT (Computed Tomography) scanners, MRI (Magnetic Resonance Imaging) apparatuses, PET (Positron Emission Thmography) apparatuses, ultrasonic diagnostic apparatuses, angiography apparatuses, MRA (MR angiography) apparatuses and the like.
When the abovementioned imaging diagnostic apparatuses are used, a liquid such as a contrast medium or physiological saline may be injected into a patient. Chemical liquid injectors for automatically performing the injection have been put into practical use. An example of such a chemical liquid injector in the related art will hereinafter be described with reference to FIGS. 8 to 10.
As shown in FIG. 8, normal syringe 10 serving as a liquid syringe comprises cylinder member 11 and piston member 12. Cylinder member 11 includes elongated cylinder body 13 in a cylindrical shape. Cylinder body 13 has a closed leading end face having hollow conduit 14 formed at the center and a trailing end having cylinder flange 15 on the outer circumference.
Piston member 12 includes elongated piston rod 17 which has piston flange 18 formed on the outer circumference of the trailing end. Piston head 19 made of an elastic member such as rubber and resin is put on the leading end of piston rod 17 and piston head 19 is slidably inserted into the interior of cylinder member 11.
Chemical liquid injector 20 illustrated herein includes one injection head 21 and two piston driving mechanisms 22. One injection head 21 has two concave portions 23 formed therein for individually holding cylinder members 11 of two normal syringes 10. Two piston driving mechanisms 22 are placed individually in the rearward section of two concave portions 23 and hold and slide piston members 12 of normal syringes 10.
More specifically, as shown in FIG. 9, piston driving mechanism 22 includes slide rod 25 slidable forward and rearward. Piston pressing member 26 is formed integrally with the front end of slide rod 25 and abuts on piston member 12 from behind. A pair of engagement hooks 27 openable or closable leftward and rightward is placed on piston pressing member 26. Engagement hooks 27 individually catch the left and right of the front surface of piston flange 19.
There are a plurality of types of normal syringes 10 to be mounted on chemical liquid injector 20. Since such normal syringes 10 of the various types have components of different sizes or shapes, the chemical liquid injection system illustrated herein includes cylinder adapter 30 prepared for each of normal syringes other than that of the maximum size.
Cylinder adapter 30 is formed to have the outer shape comparable to that of cylinder member 11 of normal syringe 10 of the maximum size and has adapter flange 31 formed on the outer circumference of the trailing end in the same shape as that of cylinder flange 15 of normal syringe 10 of the maximum size. Concave portion 23 of injection head 21 accommodates cylinder member 11 of normal syringe 10 of the maximum size and cylinder adapter 30 which are placed in the same manner. Cylinder adapter 30 accommodates cylinder member 11 of normal syringe 10 of the size fitting concave portion 32 of that cylinder adapter 30.
Besides the abovementioned normal syringe 10, rodless syringe 40 as shown in FIG. 10 is an example of the liquid syringe. In rodless syringe 40, piston member 41 comprises a piston head having no piston rod. Piston flange 42 having a small diameter is formed directly on the trailing end of the piston head.
Since normal syringe 10 typically has piston flange 18 formed to have a larger diameter than the internal diameter of cylinder member 11, piston pressing member 26 of chemical liquid injector 20 for holding piston flange 18 of normal syringe 10 is formed to have a larger diameter than the internal diameter of cylinder member 11.
Thus, piston pressing member 26 of chemical liquid injector 20 cannot enter cylinder member 11 of rodless syringe 40 and cannot press directly piston member 41 of rodless syringe 40. When such rodless syringe 40 is mounted on chemical liquid injector 20, piston adapter 50 connects piston member 41 to piston driving mechanism 22.
Piston adapter 50 includes adapter rod 51 having an about the same shape as that of piston member 12 of normal syringe 10 and has adapter flange 52 formed on the trailing end and having the same shape as that of piston flange 16. Piston adapter 50 has recess 53 formed at the leading end and receiving piston flange 42 of rodless syringe 40. Flange holding member 54 is put to be swingable for opening or closing recess 53.
In chemical liquid injector 20 of the related art with the abovementioned structure, normal syringe 10 of the maximum size is directly mounted on injection head 21, and normal syringe of a size other than the maximum size is mounted on injection head 21 with dedicated cylinder adapter 30 placed between them. Rodless syringe 10 is mounted on injection head 21 with dedicated piston adapter 50 and, as required, cylinder adapter 30 placed between them.
In use of rodless syringe 40, flange holding member 54 of piston adapter 50 is manually operated to open recess 53 to insert piston flange 42 into recess 53, and then flange holding member 54 is manually operated to close recess 53. Piston adapter 50 is mounted on piston member 41 in this manner to cause them to have an about the same outer shape as that of normal syringe 10, so that rodless syringe 40 can be put on injection head 21 of chemical liquid injector 20, such as by using cylinder adapter 30 or the like, similarly to normal syringe 10.
In this case, cylinder member 11 of rodless syringe 40 is held in concave portion 23 of injection head 21 with cylinder adapter 30 placed between them, and adapter flange 52 of piston adapter 50 connected to piston member 41 is held by piston driving mechanism 22.
Cylinder member 11 is connected to a patient through an extension tube (not shown), and piston adapter 50 is pressed by piston driving mechanism 22. Piston member 41 is pressed into cylinder member 11 together with piston adapter 50 to inject the liquid into the patient from cylinder member 11.
There are a pre-filled type and a refill type in the abovementioned normal syringe 10 and rodless syringe 40. The pre-filled type is shipped with a liquid contained therein and is used only once. The refill type is filled with a desired liquid by an operator and is repeatedly used. In normal syringe 10 and rodless syringe 40 of the pre-filled type, after piston members 12, 41 are pressed into cylinder member 11 for liquid injection, piston members 12, 41 do not need to be pulled out. Thus, it is easy to press piston members 12, 41 into cylinder member 11 in liquid syringes 10, 40 of the pre-filled type, but it is often difficult to pull them out.
Chemical liquid injectors of the type described above have been invented and applied by the present applicant (see, for example, patent documents 1 and 2). Piston adapters of the type described above also have been invented and applied by the present applicant (see, for example, patent document 3).    Patent document 1: Japanese Patent Laid-Open No. 2002-11096    Patent document 2: Japanese Patent Laid-Open No. 2002-102343    Patent document 3: Japanese Patent Laid-Open No. 2003-290346